Microbiology 1: Bacterial properties Flashcards
Name the 3 Forms of bacteria and draw them?
rod=bacillus
What is gram stain used for?
– Distinguishes between two different kinds of bacterial cell walls
-Stain indicates whether or not you have Gram-negative or Gram-positive bacteria.
Describe the steps for gram staining?
– Bacteria are stained with a violet dye and iodine, rinsed in alcohol, and then stained with a red dye.
What colour is a gram positive bacteria stained and why is it stained that colour?
Gram positive bacteria: Peptidoglycan in cell wall retains dye. High peptidoglycan = deep violet
What colour is a gram negative bacteria stained and why is it stained that colour?
Dye is lost from thinner peptidoglcan The cells absorb counterstain making them appear pink
What is the difference in the peptidoglycan of gram positive and gram negative bacteria?
Peptodoglycan in Gram posistive bacteria is much thicker than gram negative bacteria- hence gram positive can retain the dye
Is this a gram positive or gram negative cell wall structure?
Gram positive
Is this a gram positive or gram negative cell wall structure?
Gram negative
How many membranes does gram positive have and how many membranes does gram negative bacteria have?
Gram negative bacteria have TWO MEMBRANES (inner and outer)
Gram positive only have ONE MEMBRANE
THIS IS THE KEY DIFFERENCE ^
Name and describe the 3 ways bacteria survive in the host cell?
Prevent Fusion with Lysosomes - Salmonella, Mycobacteri and Chlamydia
Escape - Listeria and Shigella break down the vesicle and escape into the cytoplasm
Survive in Phagolysosome - Coxiella can just survive in the harsh environment inside a phagolysosome
What are the two related multi-protein machines required for motility and invasion?
Flagella
Injectisome
How does an injectisome cause salmonella to enter a host cell?
They polymerise actin into filaments
This ruffles the plasma membrane and bacteria get stuck in this ruffle
As the process dies down and returns to normal, the trapped bacteria is internalised
What is the function of flagella?
flagella allows the propulsion of bacteria through fluids - they are filamentous structures and they rotate and are organised as a series of rods and filaments
Name another method of invasion into a host cell?
Hint:Listeria and Shigell use this mechanism
It breaks out of the vacuole
It then assembles/polymerises actin at one pole of the bacterial cell
This polymerisation of actin generates force which propels the bacterium through the cytoplasm
This leads to the spread of the bacterium from one cell to another
These streams of actin are known as COMET TAILS
Listeria and Shigella can both do this
Name the 3 main ways bacteria use to exchange gemetic material?
Transformation
Transduction
Conjugation
Bacteria can take up DNA from the environment giving them immense potential to adapt and overcome our immune system
What is Transformation?
What is transduction?
What is conjugation?
What is a PATHOGENICITY ISLAND?
PATHOGENICITY ISLAND = Horizontally Acquired DNA that contributed to Virulence
What illness does Salmonella typhi cause?
typhoid fever
What illness does Shigella cause?
dysentery
What two illness can Neisseria cause?
meningitis, gonorrohea
What illness can Streptococcus pneumoniae cause?
Pneumonia
What illness is caused by Mycobacterium tuberculosis?
tuberculosis
Name an extracellular bacteria?
Streptococcus
Name an intracellular bacteria?
Mycobacterium
Name an obligate intracellular bacteria?
obligate intracellular parasite- Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. only show characteristics of life inside a cell
Chlamydia
What substance is only present in gram negative bacterial cell walls?
LIPOPOLYSACCHARIDE (LPS)
Where is LIPOPOLYSACCHARIDE (LPS) found on gram negative bacteria?
Which membrane?
Outer Membrane - composed mainly of LIPOPOLYSACCHARIDE (LPS)
Is Escherichia coli gram positive or gram negative?
Gram negative
Is Salmonella (typhimurium - food poisoning, typhi - typhoid) gram positive or gram negative?
Gram negative
Is Shigella Gram positive or gram negative?
Gram Negative
Is Vibrio cholerae gram negative or gram positive?
Gram Negative
Is Neisseria (meningitidis- meningitis, gonorrhoeae- gonorrhea) gram positive or gram negative?
Gram Negative
Is Staphylococcus aureus (skin diseases, endocarditis, bacteraemia, joint diseases, pneumonia) gram positive or gram negative?
Gram Positive
Is Streptococcus pneumoniae (pneumonia, meningitis, otitis media) Gram Postive or Gram Negative?
Gram Positive
Is Streptococcus pyogenes (tonsilitis, necrotizing fasciitis, bacteremia, scarlet fever) gram Positive or Gram Negative?
Gram Positive
What bacterias are neither gram positive or gram negative?
Mycobacterium tuberculosis (TB)
Mycobacterium leprae (leprosy)
What 5 things do bacteria have to do to be a pathogen?
Colonise - pili and fimbriae have formed to allow them to cling onto surfaces
Persist - ability to avoid the host defences - deal with innate immune function
Replicate - acquire nutrients needed for replication e.g. iron is limited in the body
Disseminate within cells, tissues, between organs and hosts
Cause Disease - produce toxins that kill host cells - dysregulation of host immune responses
CCPRD
Are these bacteria intracellular or extracellular?
Staphylococcus
Streptococcus
Yersinia
Neisseria
Extracellular
Are these bacteria intracellular or extracellular?
Listeria Shigella
Salmonella
Chlamydia
Coxiella
Intracellular
Motility and Invasion require two related multi-protein machines:
Name these machines?
Flagella
Type III Secretion System
What is a Type III secretion system?
Delivers virulence proteins into the host cell
IMPORTANT: bacterial virulence proteins (effectors) induce actin polymerisation, membrane ruffling and bacterial internalisation
Hence the type III secretory system is needed to deliver the effectors which allow the internalisation of the bacteria.
This needle structure is evolutionarily linked to the flagellum
Instead of making a flagellum, a bacterium can make this needle shaped structure which allows effector proteins to be injected into the host cell through translocase.
Many gram negative bacteria have this feature but NO GRAM POSITIVE BACTERIA HAVE THIS
This is a translocon which inserts into the plasma membrane of the host cell.
By making a passage into the cell, it allows effector proteins to be transferred from the bacterial cell to the host cell.
The effector proteins lead to actin polymerisation which causes the uptake of bacteria into the host cell.
This examples is Salmonella
What feature does many gram negative bacteria have, but no gram positve bacteria have?
Type III Secretion System
